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24/08/2006 IAU redefines the term "planet"

In the 1990s, astronomers began to find objects in the same region of space as Pluto, and some even farther away. Many of these shared several of Pluto's key orbital characteristics, and Pluto started being seen as the largest member of a new class of objects, plutinos. This led some astronomers to stop referring to Pluto as a planet.